facing issue while accessing server using DHCP provided DNS of firewall

hi. i have XG210 (SFOS 17.5.14 MR-14-1). it is also acting as DHCP server and giving ip to clients.in DHCP i configured DNS server of my
local server i.e, domain controller. today i start having issue the i m not able to access the server placed in my LAN. when i configure
DNS ip manually in client pc then i am able to access that website. when i configure to get ip from dhcp (in my case it is firewall) then
i m not able to browse that website. i cleared the browser cache, also tired in private browser but same issue.
please guide me how to resolve it?

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[edited by: emmosophos at 3:35 PM (GMT -8) on 30 Nov 2021]